Method for producing ammonia and boric acid



Dec. M, 1937. J. M. PETERSN METHOD FOR PRODUCING AMMONIA AND BORIC ACIDFiled May 5, 1934 .VN @N Jf//V ffm/wmv ATTORNE s Patented Dec. 14, 1937PA'rENT orFl-CE `ll/IETHOD FOR PRODUCING AMMONIA AND BORIC ACID JohnMerriam Peterson, Avondale, Pa., assignor to Hercules Powder Company,Wilmington, Del., a corporation of Delaware Application May 5, 1934,Serial No. 724,219

3 Claims.

'This invention relates to a method. for producing ammonia land. 4boricacid.

Heretofore, as is well known, ammonia, has been produce-d by reactingammonium sulphate 5 with a strong alkali as, for example, lime, with theproduction of calcium sulphate'as a waste product; while boric acid hasbeen produced by reacting borax with an acid as, for example, sulphuricacid, with the production of sodium sulphate.

Now, in accordance with this invention, Ihave found that ammonia and.boric acid canbe proi :duced by reactingan inorganic ammonium salt witha borate soluble in a solution of ammonium salts. The reaction may becarried out 4under any 'suitable "conditions and without necessity'forthe use of any particular form of apparatus. The ammonia and boric acidproduced may be recovered in any convenient manner.

In proceeding in accordance with this invention inorganic ammonium saltssuch as, for example, ammonium sulphate, ammonium chloride, `ammoniumnitrate, etc.,'etc. may be used; while water-soluble borates as, forVexample, sodium borate (borax) potassium borate, lithium berate, etc.,etc. may be used. l

The reaction involved in accordance with this invention, using, forexample, ammonium sulphate and lborax, will be as follows:

from which it will be noted that in addition to ammonia and boric acidan alkali salt of an inorganic acid, in the above reaction sodiumsulphate or salt cake adaptable for use in sulphate pulp plants, isproduced.

In practice the inorganic ammonium salt and water soluble borate may bereacted in 'aqueous solution or in substantially dry state. Generallyspeaking, heat will desirably be applied to facilitate the reaction andto facilitate recovery of the ammonia produced.

rAs illustrative of the carrying out of the process in accordance withmy invention, reference is made to the accompanying drawing,.in" which-I represents a closed tank containing an aqueous solution of ammoniumsulphate and borax, agitated by stirring device 2. Steam is admitted tothe bottom of tank I via pipe 3 and valve ll. From tank I pipe 5 leadsto condenser 6, wherein the ammonia and water vapor escaping' from tankI during the reaction are condensed to aqueous ammonia, which latterescapes from condenser 6 via pipe 1 to ammonia liquor storage tank 8.

From the bottom of tank I the solution, after completion of thereaction, is passed via valve 9 and pipe Il) into crystallizer II,cooled by cool- .V5 ing jacket I2. Crystallized boric acid fromcrystallizer II passes via large pipe I3 to centrifugalv Ill, where thegreater part of its moisture content Vis removed. From centrifugal Ibithe centrifuged crystals of boric acid are conveyed 1() Via conveyor I5to drier I6, where the boric acid crystals are dried, finally passingviaconveyor I'I to storage tank I8.

The liquid wrung from the wet boric acid crystals in centrifugal I 4passes via pipe I9 to T5 evaporator 2i), from which the mixture ofsolution and crystals, after partial q evaporation, passes via pipe ZIand valve 22 to centrifugal 23, where the sodium sulphate is removed asa solid passing via pipe 24' to drier 25, from which the dried sodiumsulphate passes via conveyor 26 to storage tank 21.

' The liquid separated in centrifugal 23 passes via pipe28to'crystallizer 29, wherein the boric acid crystallizes out, and fromcrystallizer 29 the boric acid passes Via pipe 3il to centrifugal SI, inwhich the boric acid is freed from liquid and is passed via conveyor 32to drier I6, where it joins with the boric acid rst produced. Theaqueous solution separated in centrifugal 3l .30 passes via pipe 33 andpump 34 to evaporator 2D.

As illustrative of a practical adaptation of this invention, forexample, an aqueous solution of ammonium sulphate and. borax, in themolecular proportions given above and. of any desired 35 concentration,are run down an ordinary stripping column or plate column, whileadmitting steam at the bottom of the column. If desired a vacuum may bemaintained on the column. Ammonia will pass in gaseous form from the topof 40 the tower and oncocling to condense moisture may be passed tostorage or a place of consumption. The residual solution leaving thebottom of the'tower or column and containing sodium sulphate and boricacid is cooled to precipitate a large part of the boric acid, which thenmay be readily recovered, for example, by ltration orv otherwise. It ispreferred to discontinue cooling the solution just prior to reaching thepoint of mutual solubility of boric acid and sodium sulphate to preventcontamination of the former by the latter. The mother liquor is thenconcentrated in any suitable means, for example, by l evaporation atelevated temperature, leaving solid Sodium sulphate or salt cakesuitable for use in sulphate pulp plants. It is preferred to separatesoluble borate and an inorganic ammonium salt sodium sulphate at anelevated temperature and to discontinue evaporation just prior toreaching the mutual saturation point of sodium sulphate and boric acidto prevent contamination of the former by the latter. This crystallizingcycle of separating boric acid on cooling followed by separating sodiumsulphate at higher temperature and evaporation may be repeated with theresidual liquor or the liquor may be added back to the cycle with newmother liquor.

As illustrative, for example, 3.9 parts of ammonium sulphate, (NH4)2SO4,11.3 parts sodium borate, NazBlOvlOHzO, and 5,3 partsV water are made toreact, yielding approximately 1 part ammonia, NH3. Residue is cooledapproximately to 35 C. to precipitate boric acid, H3BO3, at a yield ofapproximately Solution is then heated to about '75 C. and 4.6 parts ofwater are evaporated to precipitate 2.4 parts sodium sulphate, NazSO4 ata yield of approximately 59%. Upon cooling to 35 C. about 0.6 parts ofHaBOs is again precipitated to bring the total yield to approximately94%. Residual liquor may be placed back into the system with new liquorfollowing the rst precipitation of I-IsBOs. This example is given by wayof illustrating the process and is not to be understood as limiting theconditions or scope of operation. Y

As further illustrative of practical adaption of this invention, forexample, equivalent quantity of a'water-soluble berate and an inorganicammonium salt Vare heated in a substantially dry state in a retort. Anysuitable'temperature may be used since temperature is not the essence ofthis invention. A temperature oi, for example, C. will be desirable.Ammonia will escape from the retort and is collected in any' suitablemanner, While an alkali salt of an inorganic acid and boric acid willremain in the retort as a residue. Residue is then extracted with asolvent for boric acid, which is a non-solvent for the alkali salt asfor example, ethyl alcohol, methyl alcohol, propyl alcohol (commercialgrade), or the like. The boric acid is then recovered from the extractin any convenient manner as, for example, by distilling oi the solvent.

It will be noted that with use of Van excess of berate, say about 10%excess over the ammonia, a higher yield will be readily obtained.

It will be understood that this invention from the broad standpointinvolves the production of ammonia and boric acid by reacting awaterunder any conditions. It Will be understood that procedure with theuse of a suitable elevated temperature which will facilitate thereaction is desirable, but not essential; and it will be understood thatthe particular descriptions of practical adaptations of this inventiongiven herein are given by way of illustration and are not contemplatedas limiting upon the scope of this invention.

What I claim and desire to protect by Letters Patent is:

l. The method of producing ammonia and boric acid which includesreacting borax and ammonium sulphate in aqueous solution, collectingevolved ammonia and separating boric acid from sodium sulphate producedby alternately cooling and heating the aqueous solution of the two saltsand electing partial evaporation of water during the cycle, wherebyboric acid substantiali;

ly free from sodium sulphate is crystallized from the solution duringthe cooling step and sodium sulphate substantially free from boric acidis crystallized from the solution during the heating step.

2. The method of producing ammonia and boric acid which includes passingan aqueous solution of borax and ammonium sulphate through a tower,heating the aqueous solution in its passage through the tower,collecting ammonia gas evolved from the tower, cooling the aqueoussolution leaving the tower to about 35 C. to crystallize boric acid,recovering the crystallized boric acid, evaporating any water necessaryto saturate the solution with sodium sulphate and raising the solutiontemperature to effect crystallization of sodium sulphate, recovering thecrystallized sodium sulphate, cooling the solution again to about 35 C.to crystallize more boric acid, and recovering said crystallized boricacid.

3. The method of producing ammonia and boric acid which includesreacting borax and ammonium sulphate in aqueous solution, collectingevolved ammonia, evaporating any Water necessary to saturate the aqueoussolution with sodium sulphate and raising the solution temperature toeffect crystallization of sodium sulphate` substantially free from boricacid, recovering the crystallized sodium sulphate, cooling the aqueoussolution to effect crystallization of boric acid substantially free fromsodium sulphate and recovering the crystallized boric acid.

JOHN MERRIAM PETERSON.

